Jeff we have had the same problem in our travel trailer at the farm. I have put out about ten bait boxes with bait in them around the trailer. It seems to have been working fairly well. The only gripe I have is that the bait all gets eaten every six weeks and has to be replenished at a cost of about thirty dollars worth of bait. Even so it is still better than having mice scurrying around when you are trying to sleep. When Pam and I first got married we had no money and stayed in a log cabin in Colorodo for 18 bucks a night. The first night when we turned the lights out I thought I heard a bear in our cabin. I turned on the lights to see about twenty mice getting into our food. The next day I bought about twenty mouse traps and set them in the room. As soon as the lights went out it sounded like all of the traps went off at once. I had to reset the traps a second and a third time before we quit hearing mice. It was one of my favorite trips to Colorodo but I hate mice.
